Patent application title: PUMPING DEVICE

Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A fluid pumping device for placing inside a casing extending into a
drilling well in order to pump a fluid present in a lower zone of the
casing and delivering it to an upper zone of the casing. The fluid
pumping device comprises an assembly of cylindrical elements placed end
to end, the cylindrical elements of this assembly comprising: a seal to
cooperate with the casing to ensure a tight seal between the lower zone
and the upper zone; a hydraulic pump; an electric motor for driving the
hydraulic pump, lubricated by a hydraulic fluid; and a compensator to
balance the pressure of the hydraulic fluid lubricating the electric
motor with the pressure of the fluid in the lower zone of the casing.

Claims:

1. A fluid pumping device for placing inside a casing extending into a
drilling well to pump a fluid from a lower zone of the casing to an upper
zone of the casing, the pumping device comprising an assembly of
cylindrical elements placed end to end, the cylindrical elements of this
assembly comprising: a seal that cooperates with the casing to ensure a
tight seal between the lower zone and the upper zone; a hydraulic pump;
an electric motor lubricated by hydraulic fluid for driving the hydraulic
pump; and a pressure compensator that balances the pressure of the
hydraulic fluid lubricating the electric motor with the pressure of the
fluid in the lower zone of the casing.

2. The pumping device according to claim 1, wherein the seal is situated
at the base of said assembly; the pressure compensator comprises a
cylindrical chamber in which a free piston slides counterheld by a
spring, said free piston being in contact with the fluid to be pumped and
with the hydraulic fluid lubricating the electric motor, so as to balance
the pressure of the fluid to be pumped and of the hydraulic fluid; and
the hydraulic pump comprises two symmetrical and opposing inclined plates
mobile in rotation, and two sets of hollow axial pistons resting against
the two inclined plates, the hollow axial pistons being able to be
displaced axially by the rotational movement of the two inclined plates,
housed in cylindrical chambers able to communicate with the lower zone of
the casing and cooperating with a delivery pipeline able to communicate
with the upper zone of the casing, and arranged to draw in the fluid from
the cylindrical chambers and deliver it to the delivery pipeline on a
rotational movement of the two inclined plates.

3. The pumping device according to claim 2, wherein the pressure
compensator, the hydraulic pump and the electric motor are housed in a
cylindrical envelope, and the delivery pipeline opens to the outside of
the cylindrical envelope into a space between the casing and the
cylindrical envelope.

4. The pumping device according to claim 3, wherein the pressure
compensator comprises a cylindrical tube defining the cylindrical chamber
in which the free piston slides, and the cylindrical chambers
accommodating the hollow axial pistons communicate with the lower zone of
the casing via a cylindrical space lying between the tube of the pressure
compensator and the cylindrical envelope, said tube of the pressure
compensator comprising drillings allowing the fluid to be pumped to mix
between the tube of the pressure compensator and the cylindrical
envelope.

5. The pumping device according to claim 2, wherein the two inclined
plates are fixed to a plate drive shaft, the plate drive shaft comprising
two ends each cooperating with support bearings arranged in housings, the
pumping device comprising a hydraulic fluid housing space in which the
pressure is balanced by the pressure compensator, the hydraulic fluid
housing space comprising the support bearing housings of the drive shaft
and a drilled conduit in the drive shaft connecting the support bearing
housings.

6. The pumping device according to claim 5, wherein the electric motor
comprises a housing, a stator and a motor shaft carrying a rotor, the
motor shaft being connected in rotation to the plate drive shaft and
comprising two ends each cooperating with support bearings of the motor
shaft arranged in housings, the hydraulic fluid housing space further
comprising the support bearing housings of the motor shaft and the
housing of the electric motor.

7. The pumping device according to claim 1, further comprising: an
element anchoring the pumping device inside the casing; and a transfer
pump comprising mobile pumping elements, each cooperating with a suction
pipeline that communicates with the lower zone, and with a delivery
pipeline that communicates with the upper zone, in order to draw in fluid
from the suction pipeline and delivering it to the delivery pipeline;
wherein the hydraulic pump is a hydraulic pump with a double slope cam
comprising an internal hydraulic fluid circuit, a double slope cam mobile
in rotation, and two sets of pistons able to be displaced axially on a
rotational movement of the double slope cam, the two sets of axial
pistons extending axially on either side of the double slope cam; the
hydraulic pump being associated with the transfer pump such that a
displacement of the axial pistons of the hydraulic pump causes
pressurization of the hydraulic fluid that drives the pumping elements of
the transfer pump; wherein the electric motor driving the hydraulic pump
drives the double slope cam in rotation; and wherein the pressure
compensator balances the pressure of the fluid in the lower zone of the
casing and the pressure in the internal hydraulic fluid circuit of the
hydraulic pump.

8. The pumping device according to claim 7, wherein the double slope cam
comprises two identical and symmetrical inclined faces against which rest
respectively one or the other of the two sets of axial pistons arranged
symmetrically on either side of the double slope cam.

9. The pumping device according to claim 8, wherein the axial pistons are
hollow, each able to slide in a cylinder, the hollow axial pistons
drawing in hydraulic fluid during a suction phase and delivering
hydraulic fluid during a delivery phase, each inclined face of the double
slope cam having an intake passage arranged so as to cooperate with at
least one of the hollow axial pistons during the suction phase.

10. The pumping device according to claim 9, wherein the pumping elements
of the transfer pump are supports which are each counterheld by a spring
and each comprise a head resting against a flexible membrane under the
effect of the spring, each of the supports being associated with a
cylinder in which a piston slides so as to be displaced against the
spring when said support is subjected, via the flexible membrane, to a
pressure of the hydraulic fluid delivered into said cylinder by the
piston during the delivery phase.

11. The pumping device according to claim 9, wherein the double slope cam
comprises a plurality of drillings arranged in the body of the double
slope cam, the drillings arranged so as to cooperate with two hollow
axial pistons arranged axially on either side of the double slope cam
during a delivery phase, so as to connect the cylinders in which the two
hollow axial pistons slide through the double slope cam.

12. The pumping device according to claim 11, wherein the hollow axial
pistons each cooperate with one of the two inclined faces of the double
slope cam via a hollow stud, the diameter of each hollow stud being
greater than the distance separating two adjacent drillings.

13. The pumping device according to claim 10, wherein the hydraulic pump
has a housing comprising pipelines arranged to bring the cylinders of a
first hollow axial piston into communication with the cylinders of a
second hollow axial piston.

14. The pumping device according to claim 7, wherein the hydraulic pump
comprises a housing and the transfer pump comprises an upper pumping
stage and a lower pumping stage extending respectively on either side of
the hydraulic pump housing, each of the upper and lower pumping stages
comprising pumping elements associated with a respective piston, the
delivery pipelines opening into a common pipeline, and the suction
pipelines of the lower pumping unit communicating with the common
pipeline via a pipeline arranged along the casing of the hydraulic pump.

15. The pumping device according to claim 7, wherein the pressure
compensator comprises: a tube with an inner space communicating with the
internal hydraulic circuit of the hydraulic pump and equipped with a base
through which passes a drilling communicating with the lower zone; and a
flexible separator or free piston counterheld by a spring and receiving
firstly the pressure predominating in the drilling and secondly the
pressure predominating in the internal hydraulic circuit of the hydraulic
pump.

16. The Pumping device according to claim 15, wherein the electric motor
has a housing comprising firstly a cover through which passes a bore
communicating with the inner space of the tube, and secondly a cap
through which passes a bore communicating with the internal hydraulic
circuit of the hydraulic pump.

17. The pumping device according to claim 16, wherein the electric motor
comprises a stator and a rotor carried by a motor shaft, the cover being
provided with a bearing carrying one of the ends of the motor shaft, and
the cap being provided with a bearing carrying the other end of the motor
shaft, the motor shaft being connected to a shaft of the hydraulic pump
carrying the double slope cam.

18. The pumping device according to claim 7, wherein the seal is a
compressible seal and the anchoring element comprises catches able to be
spaced apart, the pumping device comprising a control mechanism for the
seal and the anchoring element that is mobile between a released position
and an engaged position, in which firstly the control mechanism axially
compresses the seal such that when the pumping device is placed inside
the casing, the seal is pressed radially against the inner wall of the
casing, and secondly the control mechanism exerts a force on the
anchoring element spacing the catches apart, such that when the pumping
device is placed inside the casing, the catches come to rest against the
inner wall of the casing.

19. The pumping device according to claim 18, wherein the control
mechanism is a hydraulic control mechanism and the pumping device
comprises a hydropneumatic accumulator and a distributor linked to the
hydropneumatic accumulator and to the hydraulic control mechanism, the
distributor comprising a closed position in which communication between
the hydropneumatic accumulator and the hydraulic control mechanism is
interrupted, and an open position in which communication between the
hydropneumatic accumulator and the hydraulic control mechanism is
established, in order to move the control mechanism between its released
position and its engaged position.

20. The pumping device according to claim 19, wherein the hydraulic
control mechanism is provided with a return means able to return the
control mechanism to its released position, and is linked to the
distributor such that the latter is able to move the control mechanism
into its engaged position.

21. The pumping device according to claim 19, wherein the hydraulic
control mechanism is provided with a return means able to return and hold
the hydraulic control mechanism in its engaged position, and is connected
to the distributor such that the latter is able to move the control
mechanism into its released position.

22. The pumping device according to claim 18, wherein the control
mechanism comprises a shaft carrying a guide piston and a cylinder
mounted sliding on the guide piston against a spring.

23. The pumping device according to claim 22, wherein the cylinder
comprises a first moveable stop surface and the shaft comprises a second
fixed stop surface, the anchoring element being a deformable liner
mounted on the shaft between the first movable stop surface and the
second fixed stop surface, the seal being mounted on the shaft between
the first movable stop surface and the second fixed stop surface, the
control mechanism comprising an intermediate element arranged between the
seal and the anchoring element, the intermediate element comprising a
flat surface facing the seal and a conical surface facing the deformable
liner such that when the first movable stop surface is moved in the
direction of the second fixed stop surface, the flat surface of the
intermediate element compresses the seal and spaces the deformable liner
from the anchoring element such that its catches are able to come into
engagement against the inner wall of the casing.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY

[0001] This application claims priority to French Patent Application No.
1,452,987 filed Apr. 3, 2014 and French Patent Application 1,456,483
filed Jul. 4, 2014, the disclosures of which are incorporated herein by
reference and to which priority is claimed.

FIELD OF THE INVENTION

[0002] The present invention relates to a pumping apparatus able to pump
fluid from the base of deep drilling wells, wherein these wells may have
a depth of up to about 3000 m or more, and the fluids to be pumped may be
water loaded with contaminants and pollutants.

BACKGROUND OF THE INVENTION

[0003] It is known to lower a hydroelectric pumping unit into a well,
lined by at least one tube, wherein the electric motor of such unit is
powered by means of an electric cable supplying energy from the surface.

[0004] It is also known to use what is called a transfer pump in order to
pump aggressive fluids, petrol or polluted fluids, at high pressure.

SUMMARY OF THE INVENTION

[0005] It is an object of the invention to provide a pumping device that
takes up little space so that it can be placed inside a casing of small
diameter, about 50 mm or less, and that is reliable and allows the
delivery of fluid from the well at -3000 m or more up to the surface, the
fluid being likely to be contaminated, polluted and of low viscosity.

[0006] To achieve this, according to one embodiment, the invention relates
to a fluid pumping device intended to be placed inside a casing extending
into a drilling well, in order to pump a fluid present in the lower zone
of the casing and deliver it to an upper zone of the casing, the pumping
device comprising an assembly of cylindrical elements placed end to end,
the cylindrical elements of this assembly comprising:

[0007] a seal
able to cooperate with the casing to ensure a tight seal between the
lower zone and the upper zone;

[0008] a hydraulic pump;

[0009] an
electric motor for driving the hydraulic pump, lubricated by a hydraulic
fluid; and

[0010] a compensator able to balance the pressure of the
hydraulic fluid lubricating the electric motor with the pressure of the
fluid in the lower zone of the casing, i.e. the pressure in the lower
zone of the well.

[0011] Thus the electric motor driving the hydraulic pump is placed under
a pressure equal to or slightly higher than that of the liquid to be
pumped, such that the pumping device may be arranged down to depths of
the order of -3000 m without harming the function of the electric motor.

[0012] According to one embodiment, the hydraulic pump comprises two
symmetrical inclined plates each cooperating with a set of pistons able
to be displaced axially on a rotational movement of the inclined plates.

[0013] According to another embodiment, the invention relates to a fluid
pumping device intended to be placed inside a casing extending inside a
drilling well, in order to pump a fluid present in the lower zone of the
casing and delivering it to an upper zone of the casing, the pumping
device comprising an assembly of cylindrical elements placed end to end,
the assembly of cylindrical elements comprising:

[0014] an element
anchoring the pumping device inside the casing;

[0015] a seal able to
cooperate with the casing in order to ensure a tight seal between the
lower zone and the upper zone;

[0016] a transfer pump comprising mobile
pumping elements each cooperating with a suction pipeline able to
communicate with the lower zone, and with a delivery pipeline able to
communicate with the upper zone, in order to draw fluid from the suction
pipeline and deliver it to the delivery pipeline;

[0017] a hydraulic pump
with a double slope cam comprising an internal hydraulic fluid circuit, a
double slope rotatable cam, and two sets of pistons able to be displaced
axially on a rotational movement of the double slope cam, the two sets of
axial pistons extending axially on either side of the double slope cam;
the hydraulic pump being associated with the transfer pump such that
displacement of the axial pistons of the hydraulic pump causes a
pressurization of the hydraulic fluid which drives the pumping elements
of the transfer pump;

[0018] an electric motor driving the hydraulic pump
able to drive the double slope cam in rotation; and

[0019] a compensator
able to balance the pressure of the fluid in the lower zone of the casing
and the pressure in the internal hydraulic circuit of the hydraulic pump.

[0020] Such a pumping device is particularly suited for the proposed
application. In particular, a transfer pump under high pressure by a
hydraulic pump is particularly suitable for delivering a fluid likely to
be loaded with contaminants and pollutants. Furthermore, such a hydraulic
pump with double slope cam allows delivery at high pressure while taking
up little space and having a long service life due to the balancing of
the axial forces exerted on the double slope cam.

[0021] According to preferred embodiments, such a pumping device may
comprise one or more of the following characteristics:

[0022] the
double slope cam comprises two identical and symmetrical inclined faces
against that come to rest respectively one or the other of the two sets
of pistons arranged symmetrically on either side of said double slope
cam;

[0023] the pistons are hollow pistons that are each able to slide in
a cylinder, the hollow pistons being able to draw in hydraulic fluid
during a suction phase and deliver hydraulic fluid during a delivery
phase, each inclined face of the double slope cam having an intake
passage arranged so as to cooperate with the pistons of one of the sets
of pistons during their intake phase. Such an arrangement guarantees that
on each turn of the cam, the pumping elements of the transfer pump are
returned to their initial position during the intake phase of the
piston(s) that drive them;

[0024] the pumping elements of the transfer
pump are supports which are each counter-held by a spring and each
comprise a head resting under the effect of the spring against a flexible
membrane, each of the supports being associated with a cylinder in which
a piston of the hydraulic pump slides so as to be displaced against the
spring when said support is subjected, via the flexible membrane, to a
pressure of the hydraulic fluid delivered into said cylinder by the
piston during its delivery phase;

[0025] the double slope cam comprises a
plurality of drillings arranged in the mass of the double slope cam, the
drillings being arranged so as to cooperate with two hollow pistons
arranged axially on either side of the double slope cam during a delivery
phase, so as to connect the cylinders in which the two hollow pistons
slide through the double slope cam. In other words, once suction has been
applied, the hydraulic fluid is delivered to the transfer stage by one or
more flexible membrane and its supports, through the drillings produced
in the double slope cam of the hydraulic pump. Such an arrangement allows
for a simpler and less bulky hydraulic pump;

[0026] the pistons each
cooperate with one of the two inclined faces of the double slope cam via
a hollow stud, the diameter of each stud being greater than the distance
separating two adjacent drillings. Therefore the diameter of the studs is
dimensioned so as to not allow delivered hydraulic fluid to escape;

[0027] the hydraulic pump has a housing comprising pipelines arranged to
bring the cylinders with which the pistons of one of the piston sets
cooperate, into communication with the cylinders with which the pistons
of the other of the piston sets cooperate;

[0028] the hydraulic pump
comprises a housing and the transfer pump comprises an upper pumping
stage and a lower pumping stage extending respectively on either side of
the housing of the hydraulic pump, each of the upper and lower pumping
stages comprising pumping elements associated respectively with the one
and the other of the piston sets, the delivery pipelines of the two
pumping units opening into a common pipeline, and the delivery pipelines
of the lower pumping unit communicating with the common pipeline via a
pipeline arranged along the casing of the hydraulic pump;

[0029] the
compensator comprises:

[0030] a tube with an inner space communicating
with the internal hydraulic circuit of the hydraulic pump and equipped
with a base through which passes a drilling communicating with the lower
zone; and

[0031] a flexible separator or free piston counter-held by a
spring and receiving firstly the pressure predominating in the drilling
and secondly the pressure predominating in the internal hydraulic circuit
of the hydraulic pump;

[0032] the electric motor has a housing
comprising firstly a cover through which passes a bore communicating with
the inner space of the tube, and secondly a cap through which passes a
bore communicating with the internal hydraulic circuit of the hydraulic
pump;

[0033] the electric motor comprises a stator and a rotor carried by
a motor shaft, the cover being provided with a bearing carrying one of
the ends of the motor shaft, and the cap being provided with a bearing
carrying the other end of the motor shaft, the motor shaft being
connected to a shaft of the hydraulic pump carrying the double slope cam;

[0034] the seal is a compressible seal and the anchoring element
comprises catches able to be spaced apart, the pumping device comprising
a control mechanism for the seal and the anchoring element that is mobile
between a released position and an engaged position, in which firstly the
control mechanism axially compresses the seal such that when the pumping
device is placed inside the casing, the seal is pressed radially against
the inner wall of the casing, and secondly the control mechanism exerts a
force on the anchoring element spacing the catches apart, such that when
the pumping device is placed inside the casing, the catches come to rest
against the inner wall of the casing. Then the pumping device may be
lowered in the casing without being obstructed by the friction of the
seal and/or the anchoring element against the inner wall of the casing.
Also, when the pumping device is arranged at the desired depth, a common
control device allows positioning of the seal and the anchoring element
in the engaged position. Alternatively, the pumping device may also
comprise two separate control mechanisms to control the seal and the
anchoring element;

[0035] the control mechanism is a hydraulic control
mechanism and the pumping device comprises a hydropneumatic accumulator
and a distributor connected to the hydropneumatic accumulator and to the
hydraulic control mechanism, the distributor comprising a closed position
in which communication between the hydropneumatic accumulator and the
hydraulic control mechanism is interrupted, and an open position in which
communication between the hydropneumatic accumulator and the hydraulic
control mechanism is established, in order to move the control mechanism
between its released position and its engaged position;

[0036] the
hydraulic control mechanism is provided with a return means able to
return the control mechanism to its released position, and is connected
to the distributor such that the latter is able to move the control
mechanism into its engaged position;

[0037] the hydraulic control
mechanism is provided with a return means able to return and hold the
hydraulic control mechanism in its engaged position, and is connected to
the distributor such that the latter is able to move the control
mechanism into its released position;

[0038] the control mechanism
comprises a shaft carrying a guide piston and a cylinder mounted slidably
on the guide piston against a spring;

[0039] the cylinder comprises a
first moveable stop surface and the shaft comprises a second fixed stop
surface, the anchoring element being a deformable liner mounted on the
shaft between the first stop surface and the second stop surface, the
seal being mounted on the shaft between the first stop surface and the
second stop surface, the control mechanism comprising an intermediate
element arranged between the seal and the anchoring element, the
intermediate element comprising a flat surface facing the seal and a
conical surface facing the deformable liner such that when the first stop
surface is moved in the direction of the second stop surface, the flat
surface of the intermediate element compresses the seal and spaces the
deformable liner from the anchoring element such that its catches engage
against the inner wall of the casing.

[0040] According to another embodiment, the invention relates to a pumping
device intended to be placed inside a casing extending into a drilling
well, in order to pump a fluid present in a lower zone of the casing and
deliver it to an upper zone of the casing, the pumping device comprising
an assembly of cylindrical elements placed end to end, this assembly
comprising:

[0041] a seal able to cooperate with the casing in order to
ensure a tight seal between the lower zone and the upper zone;

[0042] a
hydraulic pump;

[0043] an electric pump driving the hydraulic pump,
lubricated by a hydraulic fluid; and

[0044] a compensator able to balance
the pressure of the fluid in the lower casing zone and the pressure of
the hydraulic fluid lubricating the electric motor,

[0045] wherein the seal is situated at the base of said assembly,

[0046] wherein the pressure compensator comprises a cylindrical chamber in
which a free piston slides counterheld by a spring, said free piston
being firstly in contact with the fluid to be pumped, and secondly in
contact with the hydraulic fluid lubricating the electric motor, so as to
balance the pressure of the hydraulic fluid and the pressure of the fluid
to be pumped, and

[0047] wherein the hydraulic pump comprises two symmetrical and opposing
inclined rotatable plates, and two sets of hollow axial pistons resting
against two inclined plates and able to be displaced axially by the
rotational movement of the two inclined plates, the axial hollow pistons
being housed in cylindrical chambers able to communicate with the lower
zone of the casing and cooperating with a delivery pipeline able to
communicate with the upper zone of the casing, the hollow axial pistons
being arranged to draw in the fluid of the cylindrical chambers and
delivering it to the delivery pipeline on a rotational movement of the
two inclined plates.

[0048] According to preferred embodiments, such a pumping device may
comprise one or more of the following characteristics:

[0049] the
pressure compensator, the hydraulic pump and the electric motor are
housed in a cylindrical envelope, the delivery pipeline opening to the
outside of the cylindrical envelope into a space intended to be arranged
between the casing and said cylindrical envelope and able to communicate
with the upper zone.

[0050] the pressure compensator comprises a
cylindrical tube defining the cylindrical chamber in which the free
piston slides, and wherein the cylindrical chambers accommodating the
hollow axial pistons are able to communicate with the lower zone of the
casing via a cylindrical space lying between the tube of the pressure
compensator and the cylindrical envelope, said tube of the pressure
compensator being provided with drillings allowing the fluid to be pumped
to penetrate between the tube of the pressure compensator and the
cylindrical envelope;

[0051] the two inclined plates are fixed to a plate
drive shaft, the drive shaft comprising two ends each cooperating with a
support bearing of said drive shaft arranged in a housing, the device
comprising a hydraulic fluid housing space in which the pressure is
balanced by the pressure compensator, the hydraulic fluid housing space
including the housings of the support bearings of the drive shaft and a
drilled conduit in the drive shaft connecting said bearing housings.

[0052] the electric motor comprises a stator and a motor shaft carrying a
rotor, the motor shaft being connected in rotation to the plate drive
shaft and comprising two ends each cooperating with a support bearing of
the motor shaft arranged in a housing, the hydraulic fluid housing space
including the housings of the support bearings of the motor shaft and the
housing of the electric motor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The invention will be better understood and further objectives,
details, characteristics and advantages thereof will appear more clearly
during the following description of a particular embodiment of the
invention, which is given merely for illustration and without limitation,
with reference to the attached drawings.

[0054] FIG. 1 is a longitudinal section view of an embodiment of the
pumping device according to the present invention;

[0055] FIGS. 2 to 4 are three longitudinal section views of three
embodiments of the hydraulic pump;

[0056] FIG. 5 is a plan view of one of the two inclined faces of the cam
of the hydraulic pump;

[0057] FIGS. 6 to 9 are four longitudinal section views of the device
comprising a seal and anchoring means;

[0058] FIG. 10 is a detail view illustrating the functioning of the
transfer pump;

[0059] FIG. 11 is a longitudinal section view of the first half of the
pumping device according to a second embodiment;

[0060] FIG. 12 is a longitudinal section view of the second half of the
pumping device of FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] FIG. 1 illustrates a well P provided with a casing T, at the base
of which is a lower zone F where is situated the fluid which must be
pumped to the surface.

[0062] The pumping device is lowered to the base of the well in order to
pump the fluid present in the lower zone F and deliver it to an upper
zone G arranged above the pumping device, in order to conduct the fluid
to the surface. To allow lowering of the pumping device to the base of
the well, it is composed of an assembly of cylindrical elements placed
end to end, of diameter slightly lower than that of the casing T, which
is about 50 mm.

[0063] The pumping device comprises successively, from its lower end to
its upper end, a compensator 1, an electric motor 2, a hydraulic pump 3
driven by the electric motor 2, a transfer pump 4, a seal 60 able to
cooperate with the casing in order to ensure a tight seal between the
lower zone F and the upper zone G, and an element 62 for anchoring the
pumping device inside the casing T.

[0064] The compensator 1 allows a balance to be achieved between the
pressure of the fluid to be pumped and the pressure in the internal
hydraulic circuit of the hydraulic pump 3. The compensator 1 comprises a
tube 10 with an inner space 17 communicating with the internal hydraulic
circuit of the hydraulic pump 3, as will be explained below. The tube 10
is provided with a base 11 through which passes a drilling 12
communicating with the zone F containing the fluid to be pumped. Inside
the tube 10 is a free piston 13, or a flexible separator such as a
membrane separator for example, counterheld by a spring 14 and receiving
firstly the pressure predominating in the drilling 12, and secondly the
pressure of the internal hydraulic circuit of the hydraulic pump 3.

[0065] The other end of the tube 10 is provided with a linking piece 15
ensuring a tight joint between the tube 10 of the compensator 1 and the
housing of the electric motor 2. A bore 16 passes through the linking
piece 15 and communicates with the inner space of the housing of the
electric motor 2.

[0066] According to one embodiment, the electric motor 2 is powered via an
electric cable (not shown) lowered into the casing T and thus allowing
powering of the motor from the surface. Alternatively, the pumping device
may be provided with a battery for powering the electric motor 2.

[0067] The housing of the electric motor 2 comprises a cylindrical body
26, a cover 20 fixed to the linking piece 15 of the compensator 1, and a
cap 27 ensuring the connection of the housing of the electric motor 2 to
the hydraulic pump 3. The motor has a stator 25 and a rotor (not shown)
carried by a motor shaft 23. The cover 20 supports a bearing 24 carrying
one of the ends of the motor shaft 23, while the cap 27 supports a
bearing 24 carrying the other end of the motor shaft 23.

[0068] The cover 20 has a bore 21 communicating with the bore 16 of the
linking piece 15. The cap 27 also has a bore 28 communicating with the
inner space of the housing of the hydraulic pump 3.

[0069] As a result, the inner space 17 of the tube 10 of the compensator 1
communicates with the inner space of the housing of the hydraulic pump 3
via the inner space of the housing of the electric motor 2. These spaces
are filled with oil. Thus the internal hydraulic circuit of the hydraulic
pump 3 is pressurized, via the free piston 13 of the compensator 1 or a
compensation membrane, to the pressure of the fluid to be pumped present
in the lower zone F or to a pressure slightly greater than this.

[0070] Also, the motor shaft 23 is linked to a shaft 30 of the hydraulic
pump 3. The shaft 30 of the hydraulic pump 3 is guided in rotation by a
bearing 38 supported by the housing of the hydraulic pump 3. The shaft 30
is integral with a double slope cam 31 which actuates the pistons 32.

[0071] FIGS. 2 to 4 illustrate in detail the hydraulic pump 3 and its
relationship with the pumping elements of the transfer pump 4 according
to three embodiments.

[0072] The shaft 30 of the pump 3 is integral with the double slope cam
31. This cam 31 has two identical and symmetrical inclined faces 31 a and
31b, against which two identical and symmetrical sets of pistons 32 come
to rest. The pistons 32 are thus driven in an axial translation movement
on rotation of the double slope cam 31. A first set of pistons 32 is
arranged above the double slope cam 31 double slope cam 31 and rests
against the upper inclined face 31a, and a second set of pistons 32 rests
against the lower inclined face 3lb of the double slope cam 31. The first
and second piston sets 32 are arranged symmetrically to each other
relative to the plane of symmetry of the double slope cam 31. The forces
exerted on the cam 31 by the pistons 32 are therefore equal and opposed.
Such an arrangement allows balancing of the axial loads on either side of
the double slope cam 31, and thus gives the hydraulic pump 3 a long
service life. The heads of the pistons 32 rest against the inclined faces
31a, 31b via hydrostatically balanced studs 34.

[0073] Also, the hydraulic pump 3 comprises two barrels 39 which extend on
either side of the double slope cam 31, in which the cylinders 391 are
arranged and in which the pistons 32 slide. The pistons 32 are hollow and
thus define a suction chamber.

[0074] The transfer pump 4 comprises pumping elements each consisting of a
support 40 counterheld by a spring 41. The head of this support 40 rests
against a sealed flexible membrane 42 under the effect of the springs 41.
The flexible membrane 42 and the support 40 are subjected to the pressure
predominating in the cylinder 391, such that a movement of the piston 32
in the cylinder 391 causes a displacement of the support 40. Thus the
hydraulic fluid driven by the pistons 32 of the hydraulic pump 4 actuates
the pumping elements of the transfer pump 4, which thus draws in and
delivers the liquid from the well in balanced pressure with the delivery
pressure of the hydraulic pump 3.

[0075] When the cam 31 is driven in rotation by the shaft 3, faces 31a and
31b of the cam 31 cause a reciprocating motion of the pistons 32, during
which these draw in hydraulic fluid from the internal space 33 of the
pump and deliver it towards the pumping elements of the transfer pump 4,
and vice versa.

[0076] Thus when a piston 32 is in the delivery phase, the corresponding
support 40 is displaced against the return force of the spring 41.
However, when the piston 32 is in the intake phase, the spring 41 repels
the support 40 in the return direction and returns the support 40 to its
initial position.

[0077] Each of the inclined faces 31a, 31b of the double slope cam 31 has
an arched groove, called an intake passage 36, shown on FIG. 5. The
intake passages 36 are each arranged to cooperate with the pistons 32 of
one of the sets of pistons 32 during an intake phase. Thus on each
rotation of double slope cam 31, the cylinders 391 are again brought into
communication with the inner space of the hydraulic pump 4. Such an
arrangement is particularly advantageous in that it guarantees that, on
each turn of the cam, the supports 40 are returned to their initial
position.

[0078] Furthermore, we note on FIG. 2 that the pumping elements of the
transfer pump 4 each communicate with an intermediate pipeline 72 that
communicates firstly with an intake pipeline 440 and secondly with a
delivery pipeline 430. The intake pipeline 440 communicates with the
lower zone F containing the fluid to be pumped, and the delivery pipeline
430 communicates with the upper zone G. The intake pipeline 440 and the
delivery pipeline 430 are each provided with a non-return valve 43, 44.

[0079] When a piston 32 is in the delivery phase, the support 40 is
displaced against the return force of the spring 41, and the fluid
contained in the intermediate pipeline 72 is delivered towards the
delivery pipeline 430. However, when a piston 32 is in the suction phase,
the support 40 is returned to its initial position by the spring 41,
which causes suction of the fluid to be pumped from the intake pipeline
440 to the intermediate pipeline 72.

[0080] In the embodiment shown in FIG. 2, the transfer pump 4 comprises an
upper pumping stage and a lower pumping stage arranged on either side of
the housing of the hydraulic pump 3. The lower pumping stage comprises
pumping elements which are associated with the cylinders 391 cooperating
with the set of pistons 32 arranged below the double slope cam 31,
whereas the upper pumping stage comprises pumping elements which are
associated with the cylinders 391 cooperating with the set of pistons 32
arranged above the double slope cam 31. The delivery pipelines 430 of the
lower pumping stage and those of the upper pumping stage open into a
common pipeline 47. The delivery pipelines of the lower pumping stage
communicate with the common pipeline 47 via a pipeline 45 arranged along
the housing of the hydraulic pump 3. This embodiment therefore requires
the fluid to pass via the pipeline 45 arranged along the housing of the
hydraulic pump, which is difficult to achieve because of the small space
available. Also, this embodiment requires two pumping stages each
comprising a set of supports 40 and non-return valves 43, 44.

[0081] In the embodiment shown on FIG. 3, the hydraulic fluid delivered by
the pistons 32 of the lower set of pistons is brought into communication
via pipelines 35 with the delivery of the pistons 32 of the upper set of
pistons. In other words, each of the cylinders 391 of the lower barrel 39
cooperates with its opposing cylinder 391 of the upper barrel 39. This
means that only a single set of supports 40 with their associated
non-return valves 43, 44 is required. This embodiment however, like the
embodiment in FIG. 2, requires passages for the delivered fluid along the
housing of the pump, namely pipelines 35.

[0082] FIG. 4 illustrates the preferred embodiment. In this embodiment,
the double slope cam 31 comprises a plurality of drillings 37 provided in
the mass of the double slope cam 31 and extending axially between the
upper inclined face 31 a and the lower inclined face 31b. The drillings
are arranged to cooperate with two opposing hollow pistons 32 when these
are in the delivery phase. Then the opposing cylinders 391, extending on
either side of the double slope cam 31, are connected through the double
slope cam 31 and the hollow pistons 32 when said pistons 32 are in the
delivery phase. In other words, the delivery of the pistons 32 situated
on the lower side of the cam 31 takes place through the drillings 37 to
join the delivery of the pistons 32 situated on the other side of the cam
31.

[0083] Such an embodiment eliminates the need to provide pipelines in the
housing of the hydraulic pump 3, such as pipelines 45 or 35 of the
embodiments of FIGS. 3 and 4, which is important in view of the small
space available.

[0084] FIG. 5 is a front view of one or the other of the faces 31 a and
31b of the double slope cam 31 of the embodiment in FIG. 4. As described
above, faces 31a, 31b of the double slope cam 31 each comprise an intake
passage 36 and a series of drillings 37. The diameter of each stud 34,
creating the link between the head of pistons 32 and the double slope cam
31, is greater than the distance separating two adjacent drillings 37.
Thus the diameter of the studs is dimensioned such that communication
between two opposing studs 34 is never interrupted when they are in the
delivery phase.

[0085] FIG. 10 is a cross-section of the transfer pump 4. As already
described above, the pumping elements of the transfer pump consist of a
support 40 counterheld by a spring 41, the head of which rests under the
effect of the springs 41 against a flexible membrane 42, subjected to the
pressure predominating in a cylinder of the hydraulic pump 3. Each
support 40 is thus actuated by the pressure provided by a piston 32 of
the hydraulic pump 3.

[0086] The fluid to be drawn in surrounds the body of the transfer pump 4
as indicated with reference 48. The body of the transfer pump 4 is
therefore equipped with an intake pipeline, not shown in the
cross-section view on FIG. 10, which opens at 48. The intake pipeline
communicates with a chamber 49 provided with a non-return valve 44, said
chamber 49 communicating via a pipeline 71 with an intermediate pipeline
72 arranged between the support 40 and a delivery pipeline (not shown)
fitted with another non-return valve 43. The delivery pipeline
communicates with zone G situated above the pumping device, i.e. with the
fluid delivery zone. In one embodiment, the fluid from the well, drawn in
by the transfer pump 4, is preferably filtered by a filter arranged in
the intake pipeline.

[0087] As soon as the support 40 is repelled by the return spring 41
(intake phase of piston 32), the fluid from the well is drawn in by the
non-return valve 44. As soon as the support 40 is repelled by the
hydraulic fluid of the hydraulic pump 3 (delivery phase of the piston
32), the fluid of the well is delivered in balanced pressure with the
hydraulic fluid through the delivery pipeline via the non-return valve
43.

[0088] Furthermore, the pumping device is also provided with an anchoring
element 62, a seal 60, a mechanism 5 for controlling the seal 60 and the
anchoring element 62, a hydropneumatic accumulator 57 and a distributor
58 which are shown integrated in the pumping device assembly on FIG. 1.

[0089] The seal 60 has a function essential for the operation of the
pumping device, since it must separate the lower zone F containing the
fluid to be pumped from the zone G into which the fluid is delivered. The
seal 60 must also be able to tolerate a significant pressure difference
between the lower zone F and the upper zone G, which may be as much as
300 bar.

[0090] The seal 60 is advantageously arranged close to the upper end of
the pumping device.

[0091] The liquid to be pumped is therefore not only below the pumping
device but also in the space between the casing T and the wall P of the
well, and in the space lying between firstly the compensator 1, electric
motor 2, hydraulic pump 3 and transfer pump 4, and secondly the inner
wall of the casing T, such that the transfer pump 4 will extract the
liquid to be delivered from the space surrounding it in order to deliver
it into zone G.

[0092] Thus the various elements of the pumping device are not subjected
to the high pressure predominating in the upper zone G. Therefore the
housing of the electric motor 1 and the housing of the hydraulic pump 2
are not exposed to high pressures, so they may have smaller thicknesses
in order to promote a heat exchange between the fluid to be pumped and
the hydraulic fluid accommodated in the housing of the electric motor 2
and in the housing of the hydraulic pump 3. Moreover, this also offers
greater freedom of design in the choice of materials constituting the
housings of the electric motor 2 and the hydraulic pump 3.

[0093] In order to allow the delivery of the fluid from the transfer pump
4 to the upper zone G, the hydropneumatic accumulator 57 and the
distributor 58 are accommodated in cylindrical housings provided with
delivery pipelines 571, 578 which communicate with the delivery pipelines
of the transfer pump 4. Furthermore, the control mechanism 5 for the seal
60 and the anchoring element 62 comprises a shaft 60 which is provided
with a delivery pipeline 501 communicating with the delivery pipeline 578
and opening into the upper zone G.

[0094] The function of the control mechanism 5 of the seal 60 and the
anchoring element 62, the hydropneumatic accumulator 57 and the
distributor 58, will be described in detail in relation to FIGS. 6 to 9.

[0095] The seal 60 is a compressible seal. When the seal 60 is compressed
radially as shown on FIGS. 7 and 9, the outer periphery of the seal 60 is
pressed against the inner wall of the casing T so as to ensure a tight
seal.

[0096] The anchoring element 62 is provided with catches 64 which are able
to move apart so as to engage with the inner wall of the casing T in
order to anchor the pumping device inside the casing T. The anchoring
element 62 is able to tolerate the force generated by the pumping device
multiplied by the delivery pressure of the pumping device. The anchoring
element 62 must also ensure sufficient anchoring force to block the
pumping device in rotation during operation.

[0097] FIGS. 6 and 7 illustrate a control mechanism 5 according to a first
embodiment, while FIGS. 8 and 9 illustrate a control mechanism 5
according to a second embodiment.

[0098] The control mechanism 5 is able to be moved between a release
position shown on FIGS. 6 and 8, in which the seal 60 and the anchoring
element 62 do not cooperate with the inner wall of the casing, and an
engagement position illustrated on FIGS. 7 and 9. In the engagement
position, the control mechanism 5 firstly axially compresses the seal 60
such that its outer periphery is pressed against the inner wall of the
casing T, and secondly spaces the catches 64 of the anchoring element 62
such that they engage with the inner wall of the casing T.

[0099] The control mechanism 5 comprises a shaft 50 carrying a guide
piston 52. The control mechanism 5 also comprises a cylinder 54 mounted
slidably on the shaft 50. For this, the cylinder 54 comprises an inner
chamber which accommodates the guide piston 52 and a return spring 55.
The inner chamber of the cylinder 54 is able to be pressurised so as to
cause the cylinder 54 to slide against the return force of the spring 55.

[0100] The inner chamber of the cylinder 54 is linked to an energy
reserve, here formed by a hydropneumatic accumulator 57. The
hydropneumatic accumulator 57 is connected to the inner chamber of the
cylinder 54 via a distributor 58. The distributor 58 has a closed
position in which communication between the hydropneumatic accumulator 57
and the inner chamber of the cylinder 54 is cut, and an open position in
which this communication is established. A pipeline 59 arranged in the
shaft 50 brings the reserve of hydraulic fluid into communication with
the inner chamber of the cylinder 54.

[0101] As shown on FIG. 7, in order to move the control mechanism 5
towards its engagement position, the cylinder 54 is moved in the
direction of the upper zone G along the direction of arrow F.

[0102] Furthermore, the shaft 50 passes through the compressible seal 60
and the anchoring element 62. An intermediate element 61 is arranged
between the compressible seal 60 and the anchoring element 62. The
intermediate element 61 comprises firstly a flat surface coming to face
the compressible seal 60, and secondly a conical surface coming to face
the anchoring element 62. The intermediate element 61 is mounted sliding
on the shaft 50. The compressible seal 60, the intermediate element 61
and the anchoring element 62 are arranged between a stop surface 502
carried by the cylinder 54 and a stop surface 53 carried by the shaft 50.

[0103] The anchoring element 62 comprises a deformable lining with a
plurality of elements distributed around the shaft 50 and held by a hoop
63. At one of their ends, these elements surround the end of the conical
piece 61 and at their other end they rest against the stop surface 53.
The elements 62 may swivel around the hoop 63. The outer wall of the ends
of the elements surrounding the conical piece 61 is provided with a catch
64.

[0104] The shaft 50 is also provided with a circular ring 50a serving as a
support surface for the intermediate element 61.

[0105] The function of the control mechanism 5 described is as follows.

[0106] When the accumulator 57 releases part of its energy reserve thanks
to the distributor, it supplies the chamber of the cylinder 54 and the
thrust surface of the guide piston 52, which leads to a relative axial
movement between the cylinder 54 and the shaft 50. Because of this
relative axial movement, the compressible seal 60 is compressed between
the stop surface 502 of the cylinder 54 and the intermediate element 61.
The intermediate element 61 and the anchoring element 62 are pressed
against each other such that the pieces of the anchoring element 62
swiveling about the hoop 63 rise along the conical surface of the
intermediate element 61, which presses their catches 64 against the inner
wall of the casing T. Furthermore, the intermediate element 61 comes to
stop against the ring 50a of the shaft so as to allow compression of the
seal 60. This compression has the effect of deforming the seal 60 and
pressing it strongly against the inner wall of the casing T.

[0107] Therefore the following are achieved simultaneously: the desired
tightness between the suction zone F of the fluid to be pumped and the
delivery zone G of this fluid, and the anchoring of the pumping device
inside the casing T.

[0108] FIGS. 8 and 9 show the reverse function of that in FIGS. 6 and 7.
In fact in this embodiment, the spring 55 permanently holds the seal 60
crushed against the wall of the casing T and the catches 64 in engagement
(FIG. 9). Then to move the control mechanism 5 to its released position,
the distributor 58 is placed in its opening position so as to fill the
inner chamber of the cylinder and move the cylinder 54 against the return
force of the spring 55.

[0109] We note that although the seal 60, the anchoring element 62 and the
control mechanism 5 are particularly suited for the pumping device
described above, they may also be applied to any pumping device intended
to be anchored tightly inside a casing.

[0110] With reference to FIGS. 11 and 12, a pumping device according to
another embodiment will now be described.

[0111] As in the case of the embodiment described above, the pumping
device is lowered to the base of the well in order to pump the fluid
present in the lower zone F and deliver it to the upper zone G situated
above the pumping device, in order to conduct said fluid to the surface.
If the well has a depth of about 3000 m, the delivery pressure must be of
the order of about 300 bar. As in the case above, the pumping device is
composed of an assembly of cylindrical elements placed end to end, of a
diameter slightly less than that of the casing T which is of the order of
about 50 mm.

[0112] This pumping device comprises successively, from its lower end to
its upper end: a seal 100, a pressure compensator 200, a hydraulic pump
300 and an electric motor 400. The compensator 200, pump 300 and motor
400 are housed in a cylindrical envelope 500.

[0113] The seal 100 has the function of separating the casing T into two
zones, a low pressure zone and a high pressure zone. It is carried by a
plug 101. The means by which the seal 100 is pressed against the wall of
the casing T to ensure the tightness between the low pressure zone and
the high pressure zone are not described or shown in relation to the
second embodiment in FIGS. 11 and 12. Similarly, the element anchoring
the pump device inside the casing T is not shown. As an example, the
fluid pumping device according to this second embodiment may be provided
with a seal, an anchoring element and a control mechanism for the seal
and anchoring element which are substantially similar to those of the
first embodiment.

[0114] The pressure compensator 200 comprises a plug 201 attached to the
end of the cylindrical envelope 500 and screwed onto the plug 101. The
pressure compensator 200 also comprises a tube 202 carried by the plug
201, so as to define a cylindrical chamber 202a in which a free piston
203 slides counterheld by a spring 204. The fluid to be pumped present in
the lower zone F arrives in chamber 202a via the pipeline 210 which
passes through the plugs 101 and 201. The other part 205 of the chamber
202a is filled with hydraulic fluid and communicates with a chamber 206
provided in a cylindrical part 207, fixed inside the cylindrical envelope
500. Thus the free piston 203 is in contact firstly with the liquid to be
pumped and secondly with a housing space of a hydraulic fluid,
lubricating in particular the electric motor 400 for driving the
hydraulic pump, as will be described below.

[0115] The hydraulic pump 300 comprises two inclined plates 300a and 300b
keyed onto a shaft 302, against which the hollow axial pistons 301a and
301b rest. Plates 300a and 300b are symmetrical and have opposing slopes.
When plates 300a, 300b are driven in rotation by the shaft 302, they
oscillate in the cylindrical chambers 303a and 303b which communicate
with each other.

[0116] The inclined faces of plates 300a and 300b cause a reciprocating
motion of the pistons 301a, 301b, during which they draw fluid into the
cylindrical chambers 303a and 303b and deliver it into the cylindrical
space between the envelope 500 and the casing T via a delivery pipeline
308.

[0117] Hollow pistons 301a and 301b are held resting against plates 300a,
300b by springs 309 via studs 310. Plates 300a, 300b each comprise an
intake passage with which the opposing hollow pistons 301a, 301b
cooperate when in the suction phase. Thus the cylindrical chambers 303a,
303b are brought into communication with the interior of the hollow
pistons 301a, 301b via the passage when said hollow pistons are in the
suction phase. The hollow pistons 301a, 301b are housed in cylinders
provided in a central barrel. The central barrel is arranged between two
plates 300a, 300b. The cylinders of two opposing hollow pistons open into
a common pipeline provided with a non-return valve 311.

[0118] Because the inclined plates 300a and 300b are symmetrical and have
opposing slopes, pistons 301a and 301b have movements in opposite
directions. Furthermore, hollow pistons 301a, 301b are arranged opposite
each other such that the forces they create are balanced. The cylindrical
chambers 303a, 303b communicate with zone F containing the fluid to be
pumped via a cylindrical space between the tube 202 of the pressure
compensator 200 and the cylindrical envelope 500. The cylindrical
chambers 303a, 303b communicate with the cylindrical space between the
tube 202 and the cylindrical envelope 500 via pipelines arranged in the
support piece 314 of the bearing 304 of the drive shaft 302 of plates
300a, 300b and in the cylindrical part 207. The cylindrical space between
tube 202 and the cylindrical envelope 500 communicates with the interior
of tube 202 via a plurality of drillings 211 provided in the tube 202.

[0119] The drive shaft 302 for plates 300a, 300b is carried by two
bearings 304 and 305 situated at its two ends. Bearings 304, 305 are
arranged in housings provided in bearing support pieces 314, 315. A
pipeline 306 passes through the entire length of the drive shaft 302 for
the plates 300a, 300b.

[0120] The electric motor 400 has a stator and a motor shaft 401 carrying
the rotor (not shown). The motor shaft 401 is carried at both ends by two
bearings 402a and 402b and connected in rotation to shaft 302 of the
hydraulic pump 300. In the embodiment shown, the electric motor 400 is
electrically powered via a connection 403. Alternatively, the pumping
device may be equipped with a battery for powering the electric motor
400.

[0121] The housing space of the hydraulic fluid, under a pressure slightly
higher than the fluid to be pumped by the compensator 200, comprises the
chamber 206 arranged in the cylindrical piece 207, the housings of
bearings 304, 305 supporting the drive shaft 302, the housings of
bearings 402a, 402b supporting the motor shaft 401 and the electric motor
housing. In fact chamber 206 filled with hydraulic fluid communicates via
drillings 208, 209 with the housing of bearing 304, and via the conduit
306 drilled in shaft 302 with the housing of bearing 305, which itself
communicates with chamber 307 filled with hydraulic fluid. Said chamber
307 communicates with chamber 403 which communicates with the chamber of
bearing 402a. The spaces containing the windings of the motor 400 and its
shaft 401 are filled with hydraulic fluid which also fills the housing of
bearing 402b.

[0122] Consequently, the hydraulic fluid lubricates the two bearings 304
and 305 of the hydraulic pump and the two bearings 402a and 402b of the
motor 400. The space containing the hydraulic fluid is tightly separated
from the space containing the fluid to be pumped, via the seals 312, 313.

[0123] The envelope 500 which houses all the elements 200, 300 and 400 has
a diameter slightly smaller than that of the casing T: the cylindrical
space between the envelope 500 and the casing T receives the fluid pumped
by the pipeline 308. Furthermore, piece 404 carrying connection 403 also
has a diameter slightly smaller than that of the casing T. As a result,
the space between the envelope 500 and the casing T communicates with the
high pressure delivery zone G of the pumped fluid. This means that said
envelope 500 must be configured to be able to resist this high pressure.

[0124] The distribution of pressures in the pumping device according to
the second embodiment of the invention is as follows: the volumes formed
by the pressure compensator 200 and the chambers 303a and 303b of pump
300 are under low pressure; the cylindrical volume surrounding the
envelope 500 housing the compensator 200, the pump 300 and the motor 400
is under high pressure; the volumes containing the bearings 304 and 305
of pump and 402a and 402b of the motor are under the hydraulic fluid
pressure which is slightly higher than the low pressure because of spring
204.

[0125] The device functions as follows: when the motor 400 is powered via
its connection 403, it drives the shaft 302 which drives the oscillating
plates 300a and 300b, pistons 301a and 301b draws in the fluid to be
pumped present in the chambers 303a and 303b, and delivers it at high
pressure via pipeline 308 into the cylindrical space between the envelope
500 and the casing T, which space opens into zone G.

[0126] Although the invention has been described in connection with
several particular embodiments, it is evident that it is in no way
limited to these and comprises all technical equivalents of the means
described and their combinations if these fall within the context of the
invention.

[0127] Use of the verbs "contain", "comprise" or "include" and their
conjugate forms does not exclude the presence of forms or steps other
than those listed in a claim. Use of the indefinite article "a" for an
element does not, unless specified otherwise, exclude the presence of a
plurality of such elements.

[0128] In the claims, any reference symbol in brackets should not be
interpreted as a limitation of the claim.